Chain conformation of deacetylated beijeran calcium salt.

A well-defined X-ray fiber diffraction pattern was obtained from a stretched film of the calcium salt of a new uronic acid containing polysaccharide designated as beijeran in the deacetylated form, poly[-->3)-alpha-D-GalUA-(1-->3)-beta-L-Rham-(1-->3)-alpha-D -Glc-(1-->]. The oriented film showed no diffraction spots, indicating it to be amorphous. However, when annealed at high temperature, the film exhibited high crystallinity. All the visible reflections could be indexed in terms of a monoclinic unit cell with the following dimensions: a = 1.297; b = 1.676; c (fiber axis) = 2.509 nm; and gamma = 106.50 degrees. The length of the fiber axis and the absence of meridional reflections at any odd layer line indicate that an extended two-fold helical conformation was made up of two trisaccharide residues.